Hitchcocks Forum

Just read the posting about 650 twin air filters and performance.
It got me thinking what improvements to this engine could be made beyond the fitting of air filters etc.
It's a very nicely designed unit - inside as well as outside.
But given our hosts reputation for high quality high performance bits and pieces I wonder what could be done to encourage the most from this unit.

Good question. Is there much room for tuning this motor?
a four valve head and ohc
maybe porting high comp pistons cams

I’m sure the standard exhaust is restrictive, too.

Crying out for a draw-through mechanical supercharger? (be easier on a bullet though, you could power it from the distributor shaft).

I have fitted the free flow air filter and less restrictive silencers, I don't think that I want to go any further, if you make the engine faster you need to upgrade the brakes, the suspension, tyres, then with all the performance you need a fairing - and so so ... can we not just enjoy the bikes for what they are without trying to make them into something they are not?

Rushour wrote: ↑

Thu Feb 13, 2020 3:39 pm

can we not just enjoy the bikes for what they are without trying to make them into something they are not?

No!

"Crying out for a draw-through mechanical supercharger? (be easier on a bullet though, you could power it from the distributor shaft)."

I like the idea SW, but unfortunately there simply isn't the strength in the Bullets' timing assembly to turn a blower. I've supercharged a number of vehicles (hence my username) and can assure you that the drive forces are considerable- the tiny little press fit timing pinion on a Bullet will be the first link in a weak chain. And, we haven't considered yet the side loading the blower belt will put on the distributor bushings.....

Thinking this through, the drive could be taken directly from primary side of the mainshaft with a re-engineered alternator/pulley assembly, modified exposed primary cover and now dry clutch, etc, but the scope is arguably getting beyond any reasonable gains.

Further, definately not drawthrough- thermal management is the key to success with boost, and hot compressed intake air without intercooling is a bad place to start especially on an air-cooled engine.

Cool idea- I'm the last person to say 'no' to forced induction- but unfortunately in this case, the engineering outweighs the desire.

Rushour wrote: ↑

Thu Feb 13, 2020 3:39 pm

I have fitted the free flow air filter and less restrictive silencers, I don't think that I want to go any further, if you make the engine faster you need to upgrade the brakes, the suspension, tyres, then with all the performance you need a fairing - and so so ... can we not just enjoy the bikes for what they are without trying to make them into something they are not?

If we all kept bikes as they came out of the factory, companies like the one hosting this website might not last very long.....

And wouldn't life be boring?

Very True Wheaters very true! - and mine certainly is no longer standard, new paint job, seat, mudguards and silencers - I suppose its my old age not wanting to go much faster than the bike will do, I have no doubt that our hosts will be supplying go faster goodies for us to spend our money on very soon !

I would have thought that the easiest way to get a decent performance boost is to enlarge the engine's capacity. A kit is already available I believe, taking it to 865cc. This capacity just happens to be the same as the old air/oil-cooled Hinckley Triumphs, hardly coincidental, given who designed the new RE which is generally held to be very-under-stressed in its current form. As standard my own 865cc Thruxton produced 69bhp, so something of that order would be likely on the RE. Then again, there are rumours of the RE factory itself producing a more spirited, larger version. If they do I might be tempted but I'm afraid an A2 licence bike doesn't really appeal to me much. To go with the increased capacity it would also be advisable to improve airflow by using a better filter and to match it with free-flowing exhausts. An ECU remap would probably be needed. This is easy on the older Triumph twins like mine but on the RE would presumably need a Power Commander. On the standard Triumph a lot of owners are happy with the standard brakes and suspension, but many, like me, have upgraded both and ended up with a well-tuned, lively bike that stops and handles way better than a factory fresh bike and is a joy to ride hard. Think well-sorted 850 Norton Commando but without the constant maintenance and periodic rebuilds...